Had flown this airline for one other flight (2 flights actually with connection) and found flight attendants and food to be great. However, on our next flight sequence we had a 3 hour layover in Mumbai and there was no gate assigned to us when we got to airport after first flight. We checked the screens every 15 min but 30 min to take off still no gate listed on screens. Asked airport staff (I believe was security) if they knew what gate our plane would be coming to (we assummed it was running late since our previous flights had both been 30 min late). We showed this person out boarding pass with flight number, he called on walkie-talkie and told us A8. We waited there for a while and saw again no signage that this was out gate. We finally asked fellow people sitting around us and they told us there had been n announcement and it was actually A14. We ran but was told plane was already loaded and we could not board. We were then directed to speak with Air India counter manager who was so rude I cannot even put into words. He should have been fired on the spot the way he yelled at us making us feel like idiots for not somehow figuring this out. I have travelled to over 40 countries and my s.o. travels monthly domestically for work in US and neither of us has EVER missed a flight, so we're not dumb. We ended up having to stay in Mumbai for a night and pay for hotel (as well as having to pay for prepaid hotel in our destination city) and for a flight the next day on Jet Airways (who I DO recommend- very professional and punctual). We called customer service and spoke to toicketting people at airport as well and they were absolutely not budging on giivng us any credit/reimbursement. We will NEVER fly this airline again and I hope they go out of buisness with their poor customer service and organization